From the PBS article about evolution by Gareth Huw Davies The Life of Birds: Birds arrived comparatively late.
Birds living on small islands are highly vulnerable to extinction. Many have become flightless in the absence of natural predators, and when man arrived, with rats, cats and other animals, the birds stand little chance. Over 90% of birds that have become extinct during historical times lived on islands.
The dodo is the tragic symbol of bird extermination. This large, flightless, turkey-sized pigeon lived on the tropical island of Mauritius. A fruit-eater, it had little reason to move fast or fly. It was easy prey for man the hunter.
The sailor Volquard Iversen, shipwrecked on Mauritius for 5 days in 1662, gave the last eye witness account. He wrote: “They were larger than geese but not able to fly. Instead of wings they had small flaps, but they could run very fast.” Not fast enough, though, for human hunters, Only fossils and a few preserved specimens remain to remind us of this tragic species.